Gravel

The theme for today's Tiny Tuesday is Mineral. However the question is can gravel be considered a mineral.  Apparently the answer depends upon what  the various materials that make up the gravel are, but a working definition of the term 'mineral' is a solid, natural inorganic substance.  So I am taking that to fit each individual piece of gravel, I am happy working with that definition and I hope freespiral will accept it.
Thank you freespiral for hosting Tiny Tuesday this month.